1. Field of the Invention
The present invention relates to image processing apparatuses and methods, and programs used therewith, and, in particular, an image processing apparatus and method suitable for use in capturing still images during moving image capturing, and a program used therewith.
2. Description of the Related Art
Image capturing apparatuses, such as portable digital camcorders and digital still cameras, have become commonly used. In these image capturing apparatuses, for example, charge-transfer solid-state image sensing devices typified by charge-coupled device (CCD) sensors, and X-Y-address solid-state image sensing devices typified by CMOS (complementary metal-oxide semiconductor) sensors are used as image capturing devices.
The image capturing apparatuses include a type of apparatus having a function (image stabilizing function) in which, when vibration, such as camera shake, is applied to the apparatus during moving image capturing, the function cancels an effect of the vibration. Methods for the function include a method for moving a lens unit for the applied vibration, and a method (see, for example, Japanese Unexamined Patent Application Publication No. 2005-175581) for electronically correcting image instability due to camera shake by shifting (moving), for the applied vibration, in an effective pixel region of an image capturing device, a portion from which data of a still image used as a moving image field is read.
When an image capturing apparatus uses the method for canceling the effect of the vibration by shifting the lens unit, the image capturing apparatus includes an actuator for moving the lens unit and the size of the image capturing apparatus accordingly increases, so that power consumption is also large. Accordingly, it is common that image capturing apparatuses having the function (image stabilizing function) of canceling the effect of the vibration is configured to electronically correct image instability due to camera shake.
In addition, in recent years, there are increasing demands to capture still images during moving image capturing. When a still image is captured simultaneously with moving image capturing, as shown in FIG. 1, in an effective pixel region 11 of an image capturing device, a region 13 (hereinafter referred to as a “still image region”) from which (image) data of a still image captured during moving image capturing may be larger than a region 12 (hereinafter referred to as a “moving image region”) from which (image) data of a still image used as a moving image field is read.
As shown in FIG. 1, when the moving image region 12 is to some extent smaller than the effective pixel region 11, an excess region for correcting an effect of camera shake can be provided in the effective pixel region 11. In addition, by reducing the number of pixels of a still image used as each field so that the moving image region 12 is to some extent small, the amount of image data of the field can be reduced. Thus, a processing time for moving image capturing can be shortened. Conversely, by setting the still image region 13 to be slightly smaller than the effective pixel region 11, at the time of still image capturing, a still image can be captured with a large angle of view and high resolution.
In the case of electronically correcting a captured moving image, as shown on the left side of FIG. 2, when the position of a subject in the effective pixel region 11 is moved with time by applied vibration from the center to lower right portion of the effective pixel region 11, an image capturing apparatus detects the applied vibration and shifts a moving image region so as to cancel an effect of the detected vibration.
As shown on the left side of FIG. 2, a moving image region 21 at the start of image capturing, that is, of an initial moving image field, is located in the center of the effective pixel region 11. A moving image region 22 of the next field is shifted from the center to lower right portion of the effective pixel region 11, and a moving image region 23 of the next field is further shifted to the lower right portion of the effective pixel region 11. As described above, the moving image regions of the fields are shifted so that the effect of detected vibration is canceled. Thus, as shown in the middle of FIG. 2, image instability due to camera shake is corrected so that, in a still image of each field, the position of a subject is in the center of the still image. As a result, as shown on the right side of FIG. 2, on a display screen on which a moving image is played back and displayed, the position of the subject is in the center of the display screen, so that the subject does not look blurred for a user.
Conversely, in the case of still images, still images of a plurality of fields are not continuously displayed differently from the case of moving images. Thus, an image of the subject displayed on the display screen does not look blurred. Accordingly, when a still image is captured during moving image capturing, it is only necessary for the subject to be within the still image region 13 or to be viewed as a still image. In other words, correction of still image instability due to camera shake produces less advantage. Therefore, it is generally considered that correction of still image instability due to camera shake is less significant.